1. Field of the Invention
The present invention relates to a metal sheet pile used for earth-retaining structures, fundamental structures, bank protection structures or water cut-off walls in the civil engineering and construction fields. In particular, the present invention relates to a rolled steel sheet pile, which has a strong joint, enables high productivity, and avoids the occurrence of bending and/or warping. In addition, the metal sheet pile of the present invention provides the choice of interlocking in a plurality of ways by using a single kind of metal sheet pile.
2. Description of Related Art
There are two kinds of steel sheet piles, one of which is manufactured by cold-pressing a steel sheet. The other kind of steel sheet pile is referred to as rolled sheet pile, and is made by hot-rolling a slab. The rolled steel sheet pile is generally more than 6 mm in thickness, and is used for earth-retaining structures, fundamental structures, bank protection structures and water cut-off walls, where cross-sectional rigidity, mechanical strength and interlocking strength of the joint is required.
The rolled steel sheet pile according to the background art is usually classified into sheet pile types such as U-shaped steel sheet pile, Z-shaped steel sheet pile, hat-shaped sheet pile and straight web-type steel sheet pile. Hat-shaped sheet pile has an approximate shape similar to a U-shape, and has an end flange portion with a joint formed at an edge thereof. The end flange portion is parallel to a central flange portion of the hat-shaped sheet pile. The joints of steel sheet pile according to the background art are shaped, for example, as shown in FIG. 7(a), FIG. 7(b) and FIG. 7(c). A joint 10 shown in FIG. 7(a) is one of the most popular types of joint used for U-shaped steel sheet pile, because the joint is made by a relatively less amount of steel.
A joint 11 shown in FIG. 7(b) is typically employed for straight web-type steel sheet pile, which is used for cell-type structures, because the joint has a high strength. However, the joint of FIG. 7(b) is heavy and is inefficient with regard to steel consumption, since made of a relatively higher amount of steel.
A joint 12 shown in FIG. 7(c) is typically used for Z-shaped steel sheet pile or hat-shaped steel sheet pile, because one side of the joint portion can be flattened. However, the joint on each side of the sheet pile is asymmetric.
A rolled steel sheet pile is normally manufactured by rolling a rectangular solid slab. When the joints to be formed at both the right and left sides are different in shape and weight, the manufacturing is difficult and bending and/or warping can occur. Therefore the joint shown in FIG. 7(c) is inefficient in productivity.
Since a rolled steel sheet pile is typically used for earth-retaining structures, fundamental structures, bank protection structures and water cut-off walls in civil engineering and construction, the joint is required to be of high strength.
In the actual use of a steel sheet pile where one joint is fitted into a joint of another adjacent sheet pile, each joint is stressed because the adjacent sheet piles are forced away from each other. In view of this, the joint of a steel sheet pile is required to be strong enough to resist such a stressful force. The strength of each part of the joint is defined by a moment arm, which is calculated by multiplying a predetermined load by a distance from the respective part to a point of a load vector, and a thickness of the respective part. Since each joint shown in FIG. 7(a), FIG. 7(b) and FIG. 7(c) has a relatively long distance from the respective part, which is a point of stress concentration, to the point of the load vector, the strength of the joint must be increased by increasing the amount of steel used. In other words, the ratio of the strength to the amount of steel used must be increased substantially.